1. Field of the Invention
The present invention relates generally to a controlling technique of an ignition timing of an internal combustion engine, and more particularly, it relates to an apparatus for and method of controlling the ignition timing during cranking of the internal combustion engine.
2. Background Information
Japanese Laid-Open Patent Publication No. 6-137246 discloses a method of controlling the ignition timing of an internal combustion engine, in which the ignition timing during the cranking operation of the engine is constantly controlled on the basis of an ignition timing set to have a fixed advance angle. Then, when the engine rotating speed reaches a desired rotating speed, e.g., 500 r.p.m, the setting of the ignition timing at the fixed advance angle is terminated to commence the controlling of the ignition timing by a feedback control method. Nevertheless, in the proposed method, controlling of ignition timing of the engine is conducted by a non-feedback control method on the basis of the ignition timing of the fixed advance angle until the engine reaches the above-mentioned desired rotating speed, irrespective of a temperature rise in the combustion chamber of the engine. As a result, there is some doubt if the ignition timing during the cranking of the engine could be somewhat sifted from the optimum timing.
Also, Japanese Laid-Open Patent Publication No. 8-86236 discloses a method of controlling the ignition timing of an internal combustion engine, in which a state of combustion of fuel-air charge in the combustion chambers is monitored during cranking of the engine to detect whether or not explosion consecutively occurs in the engine after the initial explosion, and if it is detected that the consecutive explosion does not occur in the engine, the ignition timing of the engine is advanced. Further, when the detection of non-consecutive explosion lasts, temperature in the combustion chamber or chambers in which combustion takes place increases while reducing delay in firing of the air-fuel charge, and accordingly, such a condition is produced in which a requested timing of ignition is shifted toward the retard angle side. As a result, under this condition, if the ignition timing is advanced, the excessively early firing of the air-fuel charge in the combustion chamber or chambers might occur so that the engine is permitted to generate a reverse torque.
A further technical contrivance for controlling an ignition timing of an internal combustion engine is disclosed in Japanese laid-Open Patent Publication No. 2000-9006. In this technical contrivance, controlling of the ignition timing is transferred from an initial controlling mode at the time of cranking in which the ignition timing is controlled to be fixedly set at a retard angle side to an ordinary controlling mode after the cranking, and the ignition timing is gradually advanced to a desired timing of ignition during the ordinary controlling mode. Nevertheless, it should be understood that controlling of the ignition timing at the time of cranking is not changed from a conventional controlling art in which the timing of ignition is intentionally set at a retard angle side.
The above three disclosures reveal that the controlling of ignition timing during cranking of an internal combustion engine according to the prior art is based on a method in which the ignition timing is fixedly set at a generally retard angle side with respect to the engine dead center. Even when correction is made to shift the ignition timing toward an advance angle side, there is some doubt if an excessively early firing might occur in the combustion chambers of the internal combustion engine. Consequently, it is understood that an optimum controlling of ignition timing could not be successfully achieved by the prior art.
The present invention was made while taking into consideration the above-described prior art.
Therefore, an object of the present invention is to provide a method of realizing an optimum controlling of the ignition timing during cranking of an internal combustion engine while suppressing an occurrence of an excessively early ignition.
In accordance with one aspect of the present invention, there is provided an apparatus for controlling an ignition timing of an internal combustion engine, which comprises:
a starter for cranking the engine;
a microprocessor programmed to:
detect a cranking operation of said engine, and
set an ignition timing employed in the cranking operation in accordance with a parameter that represents a temperature in a combustion chamber of said engine; and
a spark plug that ignites an air-fuel mixture in the combustion chamber on the basis of the ignition timing when said engine is in the cranking operation.
In accordance with another aspect of the present invention, there is provided an apparatus for controlling an ignition timing of an internal combustion engine, which comprises:
a starter switch;
a starter, connected to said starter switch, for cranking the engine;
means for detecting a cranking operation of said engine;
means for setting an ignition timing employed in the cranking operation based on a parameter that represents a temperature in a combustion chamber of the engine; and
a spark plug for igniting an air-fuel mixture in the combustion chamber on the basis of the ignition timing when the engine is in the cranking operation.
In accordance with a further aspect of the present invention, there is provided a method of controlling an ignition timing of an internal combustion engine, which comprises:
detecting a cranking operation of said engine;
setting an ignition timing employed in the cranking operation based on a parameter that represents a temperature in a combustion chamber of said engine; and
igniting an air-fuel mixture in the combustion chamber on the basis of said ignition timing when said engine is in the cranking operation.
Namely, according to the present invention, a change in the temperature in the combustion chamber after the start of cranking operation is estimated to detect a rise in the temperature of the combustion chamber, and since a correction is applied to the ignition timing during cranking of the internal combustion engine in response to the detected temperature rise in the combustion chamber, there is no anxiety about any possibility of occurrence of excessive advance of the ignition timing during ordinary cranking operation of the internal combustion engine. Accordingly, the ignition timing can be set at an optimum timing of ignition e.g., at an ignition timing of so-called minimum advance for best torque (MBT), and therefore cranking performance of an internal combustion engine can be greatly enhanced.
The above and other objects, aspects, features and advantages of the present invention will become more apparent from the ensuing description of preferred embodiments thereof in conjunction with the accompanying drawings.